> In the United States, employers with more than 100 full-time, non-probationary employees must provide 60 days notice of most planned layoffs[0]

This seemed quite surprising to me, and from reading your reference, I don't think it's nearly as broad a protection as it seems to me like you're stating it. the law seems to apply to companies that you describe, but the types of events that they need to provide notice for don't seem like "most planned layoffs" to me; the employee guide lists the following as potentially being covered:

• A plant closing (see glossary)—where your employer shuts down a facility or operating unit (see glossary) within a single site of employ- ment (see glossary and FAQs) and lays off at least 50 full-time workers;

• A mass layoff (see glossary)—where your employer lays off either between 50 and 499 full-time workers at a single site of employment and that number is 33% of the number of full-time workers at the sin- gle site of employment; or

• A situation where your employer (see glossary) lays off 500 or more full-time workers at a single site of employment

I don't think most layoffs in the US are due to shutting down an entire office, a third of an office with at least 150 people, or 500 people from the same office. I'd expect most layoffs to either be much less concentrated in a single location or not large enough to hit the defined thresholds.

[0] https://www.dol.gov/agencies/eta/layoffs/warn [1] https://www.dol.gov/sites/dolgov/files/ETA/Layoff/pdfs/Worke...